I love these things! They make painting in a sketchbook on the go so much easier. They hold a fair amount of water, are small, durable and most importantly they don't leak so they are portable. I also like giving them to my children when they paint so we don't have to worry about mess too much. I do worry about my youngest turning every set of watercolors I give her purple but that is a different issue. Nothing will top a quality brush and a cup of clean water but having a waterbrush or two around has often meant the difference between me being able to get a sketch done or not.